Question
1) What would be the major design criteria / priority in terms of using mulch
for large scale landscaping other than price point (mall area, college campus,
or couple building landscaping at one time, 20 acres for example)?

2) Also, Is there any typical type of mulch that is used more often in large
scale landscaping?  

Answer
Hello, Koo -

There are basically two types of mulch:  Organic (bark/leaf/needle products) & Inorganic (never was alive, i.e. rocks/gravel/sand).   You asked specifically about commercial applications, so I'm NOT going to discuss gardening mulches like straw, pine needles, compost, grass clippings, etc.  There is a mulch for every soil-type and occasion.  The best thing is, they don't need water and are relatively cheap compared to lawn or shrub cover.

I know you said "other than price point", but you cannot avoid money-talk, especially when talking about such a large project.  Mulch materials availability & prices are VERY regional.  What is cheap and works well in Albuquerque may be outrageously expensive in Portland or Baltimore.  Some more exotic & regional mulches I've seen used are oyster shells, seaweed, and human hair (The Chinese have done experiments with this and it really works, but has such a "gross factor" that I can't recommend it!)  You may live in an area that is plentiful in brick dust or spare tires?  I don't know.  Re-used materials like ground-up tires & tumbled glass are quite popular these days - and you get LEED credits for using local/recycled materials.

Here, decomposed granite (also called DG, "crusher fines", "crushed stone", or 搒tone dust") is the cheapest material at about $20/yard.  Next are various rock products, depending on size, that range from $25 to $75/yard. JUST for the material.  Then you have to factor in LABOR to place it, too.  Bark mulches are easier to place by hand than stone, especially big stones (+8" and larger).  It takes a front-end loader to effectively move them around.  The cheapest material is bare dirt, but your local codes may require certain landscape coverages, as ours do (no more than 10% "inert" material).  DG works out to $0.31 - $0.50 a square foot, versus a minimum of $3 per s.f. for "living" materials cost.  It goes up in price from there, depending on what type is specified.

1 yard covers 81 square feet, at 3" deep.  If your 20-acre parcel is 15% landscaped with mulch material, you'll need to cover 130,680 square feet, or 1,210 cubic yards of mulch at 3" deep.  If you go to 4" deep or 20% landscaped area, you'll need 1,613 c.y.  At 20% landscaped or 174,240 s.f., at 4" deep you'll need 2,151 cubic yards of mulch.  Wow - It adds up quick.

Also, my calculations are assuming your 20 acres have no lawn, trees, or shrubs, JUST mulch areas.  Obviously you'll have to take those area quantities out of your estimates.  If you are only using 10% "inert" materials, the numbers are only 1/10th the amount shown.  Again, I don't know your 20-acre project. You do.

Here is a useful link for quantity estimating:
http://www.donnan.com/landscaping_bulk_quantities.htm

To what your question 1.) focused on:  Other environmental & economic considerations:  windy spots should avoid bark mulch, as areas that are prone to flooding (bark floats away!); hot locations should avoid DARK rock (excessive heating properties).  All commercial mulch areas should either be treated with a pre-emergent granular herbicide or some sort of landscape fabric (NOT black plastic).  This will increase the initial cost, but lower long-term maintenance costs.  

Here are just smatterings of materials suppliers here in North America (I tried to find ones with pictures &/or prices):

Massachusetts:  http://www.barkunlimited.com/index.htm
Ontario, Canada: http://www.greelysand.com/products.html
California: http://www.psfpinc.com/products.html
Florida: http://floridamulchonline.com
Texas: http://www.t-rocks.biz/

We use a local supplier here in Nevada, but he gets materials shipped to him from all across the country (New York "blue stone", Mexican beach pebbles, etc).  1,500 to 2,000 cubic yards of anything is worth shopping around and getting the best deal - probably directly from the regional supplier/, quarry, or mill.   A tandem dump-truck can carry approximately 20 yards per load, so you are looking at up to 70 to 100 trucks of material!!

We got a bid for $50/ton for locally-quarried NV limestone stone that I know goes for $200+/ton 500 miles away in "the big cities" of Las Vegas or LA.  Beautiful rock, but expensive to haul & you get to pay for the material yard's overhead if you buy it in Vegas.  The $1,500 in materials we'll buy for this project would cost us $6,000 anywhere else.

2.) Is there any one material used more than any other in large commercial developments?  None that I know of.  I've seen them all used on commercial projects (except the human hair!)  If I had to guess, I'd say bark mulch.  It just looks more aesthetically pleasing, but has higher maintenance & replacement cycle costs.  A mix of mulch types is actually much more pleasing to the eye.

Hope I didn't prattle on too long, and I hope it helped...~Marc